Thiophene-containing Pechmann dyes (unsaturated exo-5,5-dilactones) were easily prepared by Cu-catalyzed dehydration of the corresponding β-aroylacrylic acids. Introduction of long alkyl chains greatly enhances solubility. Isomerization of an alkyl-substituted thiophene Pechmann dye (TPD) gave the corresponding endo-6,6-dilactone. The redox and electronic properties of these new dyes were investigated by CV, UV/vis, and fluorescence spectroscopy and DFT and TD-DFT computations. Strong absorption and emission in the visible region were recorded.